Figure 4. SAL treatment suppresses light-induced ER stress and protects photoreceptors and RPEs. (A) 661W cells/RPE cells were treated with SAL (1 μM, 10 μM, 20 μM and 50 μM) and cultured under 1500 Lux light or dark conditions for the indicated times. The percentage of cell death was evaluated with PI/Hoechst staining. Scale bar=100 μm. (B) The cells were treated with SAL (20 μM for 661W cells; 10 μM for ARPE-19 cells) or vehicle and cultured under light/dark conditions for 3 days, after which the levels of ER stress markers in the whole cell lysate were determined with western blotting, and β-actin was referenced as an internal control. Three independent experiments are conducted two weeks apart. The results are presented as the mean± SEM. n (per group) =3, NS: no significance, *P < 0.05, **P < 0.01.